1. Field of the Invention
The present invention relates to an engine supporting device for a vehicle such as a snowmobile or the like.
2. Description of Background Art
Japanese Patent Publication No. Sho 61-27202 discloses a snowmobile in which front and rear portions of an engine are mounted to a vehicular body through rubber members; a reduction gear case is supported on the vehicular body separately from the engine; and power is transmitted from the engine to the reduction gear through a V-belt type transmission. Japanese Patent Laid-open No. Sho 61-295129 discloses a structure in which an engine including a power transmission system similar to that described above is connected to a reduction gear case through a damper. Japanese Patent Publication No. Hei 5-17048 disclosed a structure in which a power transmission system similar to that described above is used and an engine is connected to a reduction gear case through a link mechanism.
Incidentally, in cases similar to the above-described structures where an engine having an output shaft provided with a drive pulley and a reduction gear case having an input shaft provided with a driven pulley are separately supported on a vehicular body and a belt is wound around the drive pulley and the driven pulley, vibration is applied from the driven pulley to the engine against a drive force applied from the drive pulley side to the driven pulley.
On the other hand, it is known that an engine may be supported on a vehicular body through elastic members positioned at least at two points on front and rear sides of a crank case. However, if the elastically supporting structure is used for the above-described power transmission system, the elastic members at the front and rear mounting portions are deformable at random, and accordingly, the engine may be, at each mounting portion, turned around a mounting shaft of the elastic member and/or moved in the direction perpendicular to the mounting shaft, for example, in the longitudinal direction.
To be more specific, each mounting portion functions as a supporting point around which the engine is turned due to vibration of the engine, and also functions to move the engine in the direction perpendicular to the mounting shaft. As a result, vibration of the entire engine becomes larger, and thereby a distance between the drive pulley and the driven pulley tends to vary.
Accordingly, in the structure disclosed in Japanese Patent Publication No. Sho 61-27202 or Japanese Patent Laid-open No. Sho 61-295129, vibration of the engine cannot be suppressed, which may exert an adverse effect on accessories. Further, the configuration disclosed in the Japanese Patent Publication No. Hei 5-17048 can solve such a problem. However, it requires a high level technique in terms of the setting of a link mounting angle or the like.
To solve the above problem, according to the present invention, there is provided an engine supporting device for a vehicle in which an engine and a gear box containing a reduction gear train are separately formed and separately supported on a vehicular body. A drive pulley of a V-belt type transmission is provided on an output shaft of the engine and a driven pulley of the V-belt type transmission is provided on an input shaft of the gear box. A V-belt is wound around the drive pulley and the driven pulley. The engine supporting device includes two mounting portions supported by the vehicular body, which are provided on a crank case of the engine on front and rear sides of the drive pulley in such a manner that the drive pulley is put between the mounting portions wherein one of the front and rear mounting portions mainly functions as a supporting point around which the engine is turned due to a drive reaction force of the V-belt type transmission. The other of the front and rear mounting portions is mounted on the vehicular body by a mounting shaft through an elastic member and mainly functions as a member for absorbing the vibration of the engine by deformation of the elastic member.
In the above engine supporting device, preferably, the front and rear mounting portions are mounted on the vehicular body through front and rear elastic members respectively. One of the front and rear elastic members is higher in hardness than the other of the front and rear elastic members, or either of the front and rear elastic members is formed of a ring bush.
Further, in the above engine supporting device, preferably, the mounting portion mainly functions as a supporting point around which the engine is turned is connected to the vehicular body through a tension rod, or is connected to the vehicular body through a mounting shaft and a collar or bearing turnably supporting the mounting shaft.
Since either of the front and rear mounting portions mainly functions as a supporting point around which the engine is turned, when the engine is applied with a drive reaction force of the V-belt type transmission, the movement of the engine in the longitudinal direction of the body is restricted because the supporting point around which the engine is turned substantially lies on the extension of a belt line. In the other mounting portion, the elastic member is elastically deformed to move the engine in the direction perpendicular to the mounting shaft, to thus absorb vibration of the engine.
In this way, the main functions for suppressing vibration of the engine can be differently distributed to the front and rear mounting portions by a relatively simple structure, as a result of which the movement of the entire engine due to vibration of the engine can be suppressed and thereby a change in distance between the drive pulley and the drive pulley can be reduced.
Since vibration of the engine can be thus suppressed, vibration transmitted to accessories can also be reduced, to thereby enhance the durability and improve the riding comfort. Such an engine supporting structure can be provided without necessity of any special high level technique.
In the case where the front and rear mounting portions are connected to the vehicular body through the front and rear elastic members, if the hardness of the front and rear elastic members are different from each other, the mounting portion using the harder elastic member mainly functions as a supporting point around which the engine is turned, and the other mounting portion mainly functions to absorb vibration of the engine with the elastic member of the mounting portion being relatively largely moved in the direction perpendicular to the mounting shaft. Further, the functions can be distributed to the front and rear mounting portions with an extremely simply structure in which the hardness of the elastic members are made different from each other.
In the case where the front and rear mounting portions are connected to the vehicular body through the front and rear elastic members, if one of the elastic members is formed of the ring bush, the ring bushing is liable to mainly function as a supporting point around which the engine is turned because the ring bushing is, in general, elastically harder. Accordingly, the functions can be simply distributed to the front and rear mounting portions only by changing the form of the elastic members.
In the case where one mounting portion is connected to the vehicular body through the tension rod, the tension rod allows the engine to be turned and to be restricted in its the longitudinal movement due to vibration of the engine, and the other mounting portion can absorb vibration of the engine by elastic deformation of the elastic member.
Further, in the case where one mounting portion is connected to the vehicular body not through the elastic member but through the mounting shaft and the collar or bearing for turnably supporting the mounting shaft, the mounting shaft of the mounting portion acts as the center of the turning of the engine and thereby the position of the turning center of the engine can be kept constant, and the other mounting portion can absorb vibration of the engine by elastic deformation of the elastic member.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.